NEIL LENNON has predicted that the Green Brigade -- Celtic's ultras -- will behave at the Nou Camp tonight as the team completes their Champions League group campaign.

However, the former Northern Ireland international has detected an ominous change in the group's attitude and behaviour during his tenure as manager, culminating in the vandalism that erupted at Fir Park last Friday and which prompted the club to declare precautionary bans on 128 supporters.

The trouble in Motherwell was the latest episode in a series of incidents that have seen Celtic reported to the Scottish League and charged by UEFA for the Green Brigade's display of political banners at home fixtures.

"It's very disappointing because they have added something spectacular to the stadium in terms of atmosphere, but in the last two or three years, you've felt a change," said Lennon.

"I don't know what the right word would be -- it's been a sort of powder keg. I don't like to see flares and I don't like seeing smoke bombs. I don't think they bring anything to the game and obviously the damage done at Fir Park is not like us.

"I have been disappointed at some of the antics. There is a rogue element in there -- whatever you want to call it. They set a different agenda. It's not fair on the majority, who are magnificent."

More immediately, Lennon's conundrum is how to defuse the menace of Barcelona, who need a single point to be certain of finishing top of Group H.

Tonight's encounter will be the fourth time that Lennon's Bhoys have faced the Catalan maestros in the space of 15 months.

Although Celtic went out of Europe when they lost at home to AC Milan last month, all of the games against Barcelona have been closely contested -- each has been won by a single goal -- with Barca claiming two victories, while the Hoops prevailed in last year's epic match at Parkhead.

"We have played very well in the three previous games and there is no reason we cannot do that again," said Lennon.

"The players know what's required. I hope they don't think they are coming here just to fulfil a fixture because they're not. If that's the case, they'll be in for very rough night, very early."

Emilio Izaguirre picked up his third booking against AC Milan in the last Group H fixture and will miss the game but Lennon welcomes back right-back Adam Matthews, who is contention after recovering from shoulder surgery which kept him out for seven weeks.

Skipper Scott Brown also returns after missing the last three European games through suspension, following a clash with Barca star Neymar at Parkhead.

Celtic have only scored two goals in the group so far, both in the 2-1 win over Ajax at Parkhead, and Anthony Stokes is hoping to get the chancde to make amends tonight.

"We just haven't taken our opportunities in front of goal," he admitted. "We have played good football and competed very well in the games but we haven't been as ruthless as we were last season -- it's as simple as that.

"We are obviously disappointed that there is not more to play for in Barcelona but it is still a massive game.

"We want to go out on a positive note. It will be a difficult task but we will try our best to win the game."

Lionel Messi is still unavailable for Barca, but they will be reinforced by the return of Xavi and Andres Iniesta.

Asked where the pair ranked in the football pantheon, Lennon replied: "The best -- Xavi in particular could buy himself time through his awareness on the pitch. He was never under pressure.

"The minute he got the ball he knew how to move his body into position to find a pass or find someone. He has been doing it for the last 10 to 12 years at the highest level and the two of them are just wonderful to watch.

"The speed of thought, the speed of mind, the speed of pass -- it's second to none really."

Without even the Europa League to provide a diversion after Christmas, Celtic are playing for pride and -- if they can wrest a point from one of the most unpromising venues anywhere -- a little financial solace.

The thought they do not care to entertain is that, such is the hazardous nature of the summer qualifiers -- and Celtic will again have to negotiate three sets of ties just to reach the group stage next summer -- there is no certainty about when they might compete at this level again.

Tonight's occasion, then, is to be savoured, as far as Barca will permit such a sensation.

"It's like a cup final almost -- you want to enjoy the occasion but you only do that if you play well and get something from the game," said Lennon.